考虑高温蠕变特性和残余应力的高强度钢柱抗火性能研究

With the wide application of high strength steel structures, there is great significance in theory to study fire resistance of high strength steel structures. Creep and residual stress at elevated temperature have great effect on structural response of steel members in fire. However, studies on fire resistance of high strength steel structures considering both factors are very limited. The object investigated in this project is high strength steel columns. The main variables in this study include creep property and residual stress at elevated temperature. Fire resistance of high strength steel columns will be studied by taking creep property and residual stress at elevated temperature into consideration. Creep property of high strength steel will be investigated by experiment. Based on the existed creep models, the coefficients of these models will be determined. Residual stresses in welded high strength steel section after fire exposure will be tested and the results of the test will be used to validate established finite element thermal-mechanical coupling model. The calibrated model will be employed to analysis residual stress distribution at elevated temperature and to establish residual stress model. Fire resistance analysis theory for high strength steel columns will be established by introducing creep model and residual stress model. Feasible solving methods will be explored for the theory. Experimental study on creep response of high strength steel columns at high temperature will be carried out to evaluate proposed theory and then the load bearing capacity at elevated temperature, critical temperature and fire endurance will be analyzed. Finally, fire resistance design method on high strength steel columns will be proposed and validated by standard fire test on high strength steel columns. The results of the study have great scientific significance to reveal creep property at elevated temperature and residual stress distribution and to clarify fire resistance of high strength steel columns, and provide basis for fire resistance design of high strength steel columns.

随着高强度钢结构的广泛应用，研究其抗火性能具有重要理论意义。钢材高温蠕变和截面高温下残余应力对钢构件火灾中结构响应产生较大影响，但考虑二者的高强度钢结构抗火研究较少。本项目以高强度钢柱为研究对象，以高温蠕变和残余应力为主要变量，研究考虑蠕变和残余应力的高强度钢柱抗火性能。通过试验研究高温蠕变特性，结合已有蠕变模型，确定模型参数；进行高温后截面残余应力测试，验证建立的有限元热力耦合分析模型，进而模拟高温下残余应力并建立分布模型；引入蠕变模型和残余应力模型建立高强度钢柱抗火分析理论，通过高强度钢柱高温下的蠕变变形试验验证建立的抗火理论，进而分析高强度钢柱火灾下承载力、临界温度和耐火极限并提出抗火设计方法，通过高强度钢柱标准升温下耐火试验对抗火设计方法进行验证。研究成果对揭示高强度钢高温蠕变特性和截面高温下残余应力分布、阐明高强度钢柱的抗火性能具有重要科学意义，为高强度钢柱抗火设计提供依据。

项目对高强度钢材进行了高温下和高温后力学性能试验和蠕变试验，获得了钢材不同温度下的应力-应变关系和蠕变曲线，得到了屈服强度、抗拉强度、弹性模量等参数随温度的变化规律以及蠕变应变随应力水平、温度和时间的变化规律；以试验数据为基础，建立了材料力学性能参数与温度的关系公式和高温蠕变模型。对高强钢焊接截面进行了常温下及受火后的残余应力测试，获得了残余应力的分布规律及受火温度对残余应力幅值的影响规律，建立了精细化有限元模型对焊接残余应力及高温下残余应力的释放行为进行了模拟，获得了温度变化过程中残余应力的衰减系数。对高强钢柱进行了耐火试验和蠕变屈曲试验，得到了火灾下钢柱的受力性能、结构响应和蠕变屈曲效应，建立了有限元模型对多参数影响下结构的抗火性能进行了系统分析，揭示了多个关键参数对耐火性能的影响机理，提出了考虑蠕变效应和残余应力影响的高强度钢柱抗火设计理论。项目执行中，项目组成员参加16次学术会议，其中境外国际会议4次，做邀请报告9次，大会报告6次。项目成果共发表期刊论文19篇，其中SCI收录10篇，EI收录5篇；出版英文专著1本，由Elsevier出版社出版；获授权发明专利2项，实用新型专利3项；参编行业标准1部。培养硕士研究生8名，博士研究生2名。项目很好地完成了预期目标。研究成果为提高我国高强度钢结构抗火分析和设计水平提供了理论依据，为高强钢结构的设计评估和推广应用提供了技术支撑。